Oxide Wearout, Breakdown, and Reliability

Abstract

The subject of oxide wearout, breakdown, and reliability will be reviewed, largely, from an historical perspective. Five topics will be discussed: oxide breakdown, oxide leakage currents, trap generation, statistics, and reliability. An early model of oxide breakdown, developed by Klein and Solomon, will be described and will be shown to be generally applicable to oxides manufactured today, and to other solid insulators, as well. Both hard and soft breakdowns were included in this model and will be discussed here. The importance of stressinduced-leakage-currents (SILCs) and direct tunneling currents will be discussed in the context of device applications, thinner oxides, and oxide reliability. The diminishing importance of breakdown in ultra thin oxides in ultra small devices will be contrasted with the increasing importance of oxide leakage currents. Trap generation is important in the triggering of breakdown and in the formation of SILCs. Trap generation will be discussed in some detail. Various statistical formulations of oxide breakdown, and how these distributions are related to trap generation, will be discussed. All of these effects will be related to oxide reliability and oxide integrity. An extensive bibliography has been included to help the reader obtain more detailed information concerning the concepts being discussed. Int. J. Hi. Spe. Ele. Syst. 2001.11:617-718. Downloaded from www.worldscientific.com by UNIVERSITY OF VIRGINIA on 04/10/15. For personal use only. Int. J. Hi. Spe. Ele. Syst. 2001.11:617-718. Downloaded from www.worldscientific.com by UNIVERSITY OF VIRGINIA on 04/10/15. For personal use only. Oxide Wearout, Breakdown, and Reliability 619found in an early review paper [20]. This wearout/breakdown model will be referred to as the "Klein/Solomon" model below when comparisons with modern works are needed.The Klein/Solomon model has been refined and confirmed continuously from the 1970s through the present time [10,20,. The extent of the damage is determined both by the 1/2 CV 2 energy stored in the capacitor and by the rate at which this energy discharges through the local hot spot [10,20,75,82,83,88,92,93,96,[100][101][102]. The local hot spot is often accompanied by light emission, in many cases incandescence [8-10, 103-115]. Several techniques have been developed for using the damage introduced during the breakdown to study the breakdown process [80,[116][117][118][119][120][121][122][123][124]. During the breakdown event, the stored energy in the capacitor, 1/2 CV 2 , partially discharges through the breakdown region in a time limited by the impedance of the total measurement system [8][9][10][82][83][84][85].The local breakdowns are intimately coupled to the trap generation and various trap generation models will be discussed in a separate section.During the breakdowns described by Klein/Solomon, one of two scenarios is possible during and following a breakdown discharge. Which scenario takes place depends on the oxide thickness, the oxide area, the magnitude of the stored energy, the ...

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